TEL AVIV – In a discovery that sounds like something out of science fiction, an international team of Israeli researchers has found that female moths can "hear" the ultrasonic sounds emitted by stressed plants and use this information to decide where to lay their eggs. The groundbreaking study, led by Tel Aviv University, provides the first concrete evidence of acoustic communication between plants and insects, revealing a hidden layer of interaction in the natural world.
The findings, published in the prestigious journal eLife, build on previous research from the same team which discovered that plants under stress—such as from dehydration or being cut—emit high-frequency sounds beyond the range of human hearing. The new study confirms that moths, a major agricultural pest, are not only capable of detecting these distress calls but actively change their behavior in response, a revelation that could have significant implications for agriculture and our fundamental understanding of ecology.
The Backstory: When Plants "Scream"
To understand the significance of this discovery, it's essential to revisit the team's previous work. In a landmark 2023 study, the researchers demonstrated for the first time that plants are not the silent organisms we perceive them to be. Using specialized microphones, they recorded tomato and tobacco plants emitting ultrasonic "clicking" sounds when faced with stress.
These sounds, which are too high-pitched for human ears, are well within the hearing range of many animals, including insects, rodents, and bats. This led the researchers to a critical question: if plants are broadcasting their state of health, is anyone in the animal kingdom listening and acting on that information? The new study sought to answer this by focusing on a moth's decision of where to lay its eggs.
An Elegant Experiment: Proving a Hidden Sense
A female moth's primary goal is to lay her eggs on a healthy, thriving plant that can provide ample food for her larvae when they hatch. The researchers designed a series of clever experiments to determine if moths use the plants' ultrasonic distress calls to avoid making a bad decision.
Test 1: Sound vs. Silence
In the first experiment, the scientists completely isolated the sense of sound. They placed female moths in a controlled environment with two acoustically sealed boxes. One box had a speaker playing the recorded ultrasonic distress sounds of a dehydrated tomato plant, while the other was completely silent. Surprisingly, the moths showed a clear preference for the box with the sound, likely interpreting it as a definitive sign of a living plant. To confirm this was a response to sound, they repeated the experiment with moths whose hearing organs had been blocked. In this case, the moths showed no preference.
Test 2: A Real Choice
The second experiment was designed to mimic a more realistic scenario. The moths were presented with two identical, healthy tomato plants. However, a speaker was placed next to one of the plants, playing the distress sounds. The results were decisive: the female moths consistently avoided the healthy plant associated with the distress sounds, choosing to lay their eggs on the silent, "safer" plant.
Test 3: Plant Sounds vs. Male Moth Sounds
In a final test, females were offered a choice between a silent box and a box containing male moths, which also produce ultrasonic sounds. The moths showed no preference, confirming their decision-making process for egg-laying is specifically tuned to the acoustic signature of a plant.
A New Dimension of Ecology: The Implications
This discovery fundamentally changes our understanding of the relationship between plants and animals. It shows that plants are not merely passive victims but are active communicators in their ecosystem.
The potential applications of this knowledge are significant, particularly for agriculture:
- Eco-Friendly Pest Control: It may be possible to develop devices that emit plant-distress frequencies over crops, acting as a natural "repellent" without the need for chemical pesticides.
- Smart Farming: Monitoring the acoustic emissions of crops could become a new tool for farmers to get an early warning of drought or disease stress before visible symptoms appear.
The study concludes that acoustic interactions in nature are far more widespread than previously imagined. For centuries, we have studied the visual and chemical signals in nature, but this research proves that there is a rich world of sound-based communication that we are only just beginning to understand.